A semiconductor device is one of electronic components that realize electronic devices (such as a power device, a light emitting device, a light receiving device, and so forth) on a predetermined substrate through semiconductor process techniques. For example, in the power device, a transistor, a Metal-Oxide Semiconductor Field Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT), or the Schottky diode is realized on a substrate. In the light receiving device, a photovoltaic cell or a photo sensor is realized on a substrate.
Especially, because of excellent physical and chemical characteristics, a III-V nitride semiconductor such as GaN receives great attention as a core material of a light emitting device such as a light emitting diode (LED) or a laser diode (LD). The LED or LD using the III-V nitride semiconductor is mainly used for a light emitting device in order to provide light in a blue or green wavelength range. The light emitting device is now applied to light sources of various products such as a scoreboard, and a lighting device. The III-V nitride semiconductor is typically formed of GaN-based material having an empirical formula of InXAlYGa1-X—YN (0<X, X+Y<1).
FIG. 1 is a cross-sectional view of a typical nitride light emitting device.
Referring to FIG. 1, the nitride light emitting device includes a GaN buffer layer 110, an n-type clad layer 120, an active layer 130 having a single quantum well (SQW) structure of InGaN or a multi-quantum well (MQW) structure of InGaN, and p-type clad layer 140, which are sequentially stacked on a sapphire substrate 100 (i.e., light transmitting substrate). At this point, a portion of the p-type clad layer 140 and the active layer 130 is removed through mesa etching, such that the top portion of the n-type clad layer 120 is partially exposed. Additionally, an n-type electrode 170 is formed on the exposed top portion of the n-type clad layer 120, and a transparent conductive layer 150 formed of ITO and a p-type electrode 160 are sequentially stacked on the p-type clad layer 140. Additionally, the GaN buffer layer 110 is generally formed with a thickness of several nm.
However, disadvantages such as stress and crystal defect caused by a difference of crystal lattice in each layer cannot be resolved in a typical heterogeneous substrate. Due to this, an electronic device (esp. a light emitting device)'s characteristics such as ElectroStatic Discharge (ESD), breakdown voltage, leakage current are deteriorated, which results in a decrease in the reliability of product yield and life time.
Additionally, when a nitride semiconductor device typically includes a nitride semi-conductor layer having a thickness of 5 μm or more on a heterogeneous substrate, substrate bow or warpage occurs severely. This makes it difficult to perform subsequent manufacturing processes such as substrate alignment, a photolithography process, and an etching process.